86 lines
2.7 KiB
C
86 lines
2.7 KiB
C
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// Nintendo Game Boy sound hardware emulator with save state support
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// Gb_Snd_Emu 0.1.4
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#ifndef GB_APU_H
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#define GB_APU_H
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#include "gb_oscs.h"
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// Clock rate sound hardware runs at
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enum { clock_rate = 4194304 * GB_APU_OVERCLOCK };
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// Registers are at io_addr to io_addr+io_size-1
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enum { io_addr = 0xFF10 };
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enum { io_size = 0x30 };
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enum { regs_size = io_size + 0x10 };
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enum gb_mode_t {
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mode_dmg, // Game Boy monochrome
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mode_cgb, // Game Boy Color
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mode_agb // Game Boy Advance
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};
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// 0: Square 1, 1: Square 2, 2: Wave, 3: Noise
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enum { osc_count = 4 }; // 0 <= chan < osc_count
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struct Gb_Apu {
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struct Gb_Osc* oscs [osc_count];
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blip_time_t last_time; // time sound emulator has been run to
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blip_time_t frame_period; // clocks between each frame sequencer step
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double volume_;
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bool reduce_clicks_;
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struct Gb_Square square1;
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struct Gb_Square square2;
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struct Gb_Wave wave;
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struct Gb_Noise noise;
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blip_time_t frame_time; // time of next frame sequencer action
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int frame_phase; // phase of next frame sequencer step
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uint8_t regs [regs_size];// last values written to registers
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// large objects after everything else
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struct Blip_Synth synth;
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};
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// Basics
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// Initializes apu
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void Apu_init( struct Gb_Apu* this );
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// Emulates to time t, then writes data to addr
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void Apu_write_register( struct Gb_Apu* this, blip_time_t t, int addr, int data ) ICODE_ATTR;
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// Emulates to time t, then subtracts t from the current time.
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// OK if previous write call had time slightly after t.
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void Apu_end_frame( struct Gb_Apu* this,blip_time_t t ) ICODE_ATTR;
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// More features
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// Emulates to time t, then reads from addr
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int Apu_read_register( struct Gb_Apu* this, blip_time_t t, int addr ) ICODE_ATTR;
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// Resets hardware to state after power, BEFORE boot ROM runs. Mode selects
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// sound hardware. If agb_wave is true, enables AGB's extra wave features.
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void Apu_reset( struct Gb_Apu* this, enum gb_mode_t mode, bool agb_wave );
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// Same as set_output(), but for a particular channel
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void Apu_set_output( struct Gb_Apu* this, int chan, struct Blip_Buffer* center,
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struct Blip_Buffer* left, struct Blip_Buffer* right );
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// Sets overall volume, where 1.0 is normal
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void Apu_volume( struct Gb_Apu* this, double v );
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// If true, reduces clicking by disabling DAC biasing. Note that this reduces
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// emulation accuracy, since the clicks are authentic.
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void Apu_reduce_clicks( struct Gb_Apu* this, bool reduce );
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// Sets frame sequencer rate, where 1.0 is normal. Meant for adjusting the
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// tempo in a music player.
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void Apu_set_tempo( struct Gb_Apu* this, double t );
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void write_osc( struct Gb_Apu* this, int reg, int old_data, int data ) ICODE_ATTR;
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#endif
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